Loading 3DS Files
by P.P.A.Narayanan

So, you have your 3D engine (written in D3DIM or OpenGL) up and running, but you only have 2 or 3 cubes or spheres on the screen. Time to add some more complex models. The code below listed can be used to load a 3D Studio R3 or higher .3DS files. The code loads only the vertex data, face data and materials. It ignores all other information (like camera, light, keyframe data etc), since for my purposes, I only need the mesh loaded.

If you think the code is written badly, I don't care! because it does the job and it was my desperate attempt to load some mesh into my D3DIM 3D Engine. But the code is (I hope!) simple and self explanatory for an average C/C++ programmer (or for that matter any programmer who can read C/C++ code). I have added some comments, see if it helps you. The code reads the .3ds file and creates a material list and mesh object list. The material list contains all the materials used by the mesh. The mesh contains references to the material in the material list (i.e the name).

The flag present along with face data gives the order of the faces for calculating face normals. Only the first (I think!) 3 bits are used. The code ignores the flag because I don't need it, but if you figure out the use of that flag, please let me know. Ignoring the flag in some files inverts the face normals for some faces, so it becomes invisible. But other files it works okay.

BTW the transformation matrix contains the local axis and local origin (if it is of any use 2 you).

If you have any questions about the code, or info about how to load camera/lights and other things.... you can contact me at digicrush_ii@rediff.com.

Note: You'll need to modify the code in order to make it work with your engine. I had to cut this out of a project that I am working on, so it might or might not compile right away... If anyone else out there is developing a 3-D engine and wants to share code/ideas, feel free to e-mail me at digicrush_ii@rediff.com. (FYI I'm using Visual C++ 6.0 with DX7.0)

Happy rendering!

By P.P.A.Narayanan (DiGiTaL-CrUsHeR) (digicrush_ii@rediff.com)

Download the code, or see it below.

// Copyright (c) 2000. Aanand Narayanan.P.P
// For questions email digicrush_ii@rediff.com
// Reads a .3ds file and create a linked list of objects
#include <windows.h>
#define D3DOVERLOADS
#include <d3d.h>

typedef struct _map_list
{
  char filename[256];  // Mapping filename (Texture)
  float u;             // U scale
  float v;             // V scale
  float uoff;          // U Offset
  float voff;          // V Offset
  float rot;           // Rotation angle
  _map_list *next;
}map_list;
typedef struct _mat_list
{
  char name[200];  // Material name
  DWORD ambient;   // Ambient color (RGBA)
  DWORD diffuse;   // Diffuse color (RGBA)
  DWORD specular;  // Specular color (RGBA)
  _map_list *htex, *ttex;    // Texture maps (presently only 1 is used. diffused map)
  _mat_list *next;
}mat_list;
typedef struct _face_mat
{
  char name[200];// Material Name
  WORD ne;       // No. of entries
  WORD *faces;   // Faces assigned to this material
  _face_mat *next;
}face_mat;
typedef struct _mesh_object
{
  char name[200];   // Object name
  float *vlst;      // Vertex list
  WORD *flst;       // Face list
  WORD nv;          // No. of vertices
  WORD nf;          // No. of faces
  WORD mnv;         // No. of vertices having mapping coords.
  float *mc;        // Mapping coords. as U,V pairs (actual texture coordinates)
  float lmat[4][4]; // Local transformation matrix
  _mesh_object *next;  // Pointer to the next object
  face_mat *fhead, *ftail;
}mesh_object;


char temp_name [100];
float trans_mat [4][4]; // translation matrix for objects
FILE *bin3ds;
mesh_object *head=NULL, *tail=NULL;
mat_list *mathead=NULL, *mattail=NULL;
map_list *maphead=NULL, *maptail=NULL;

void ReadObject();

unsigned char ReadChar (void)
{
 return (fgetc (bin3ds));
}
unsigned int ReadInt (void)
{
 unsigned int temp = ReadChar();      
 return ( temp | (ReadChar () << 8));  // I really don't know Y I'm do'n this, too lazy to change
}
unsigned long ReadLong (void)
{
 unsigned long temp1,temp2;

 temp1=ReadInt ();
 temp2=ReadInt ();

 return (temp1 | (temp2 << 16)); // same as above
}
void read_mat(DWORD len)
{
  unsigned long count=ftell(bin3ds) + (len - 6);
  WORD id;
  DWORD llen;
  int done = 0;
  BOOL is_ambient = FALSE;
  BOOL is_diffuse = FALSE;
  BOOL is_specular = FALSE;
  // Allocate a new material
  if(mathead == NULL)               
  {
    mathead = new mat_list;
    mattail = mathead;
  }
  else
  {
    mattail->next = new mat_list;
    mattail = mattail->next;
  }
  mattail->next = NULL;
  mattail->htex = NULL;
  while(!done)
  {
    id = ReadInt();
    if(feof(bin3ds)) // OOPS! EOF
    { 
      done = 1;
      break; 
    }
    llen = ReadLong();
    switch(id)
    {
    case 0xA000:
      {
        int i=0;
        char ch;
        mattail->next = NULL;
        // Read material name
        while((ch = fgetc(bin3ds)) != 0)
        {
          mattail->name[i] = ch;
          i++;
        }
        mattail->name[i] = '\0';
      }break;
    case 0xA010:
      {
        // Hey! AMBIENT
        is_diffuse = FALSE;
        is_specular = FALSE;
        is_ambient = TRUE;
        mattail->ambient = 0;
      }break;
    case 0xA020:
      {
        // Hey! DIFFUSE
        is_diffuse = TRUE;
        is_specular = FALSE;
        is_ambient = FALSE;
        mattail->diffuse = 0;
      }break;
    case 0xA030:
      {
        // OH! SPECULAR
        is_diffuse = FALSE;
        is_specular = TRUE;
        is_ambient = FALSE;
        mattail->specular = 0;
      }break;
    case 0xA200:
      {
        // Texture
        if(mattail->htex == NULL)
        {
          mattail->htex = new _map_list;
          mattail->htex->next = NULL;
          mattail->ttex = mattail->htex;
        }
        else
        {
          mattail->ttex->next = new _map_list;
          mattail->ttex = mattail->ttex->next;
          mattail->ttex->next = NULL;
        }
        mattail->ttex->u = mattail->ttex->v = mattail->ttex->uoff = mattail->ttex->voff = 0.0;
        mattail->ttex->rot = 0.0;
      }break;
    case 0xA300:
      {
        // Texture name (filename with out path)
        char ch;
        int i=0;
        while((ch = fgetc(bin3ds)) != 0)
        {
          mattail->ttex->filename[i] = ch;
          i++;
        }
        mattail->ttex->filename[i] = '\0';
      }break;
    case 0xA354:
      {
        // V coords
        fread(&(mattail->ttex->v), sizeof(float), 1, bin3ds);
      }break;
    case 0xA356:
      {
        // U coords
        fread(&(mattail->ttex->u), sizeof(float), 1, bin3ds);
      }break;
    case 0xA358:
      {
        // U offset
        fread(&(mattail->ttex->uoff), sizeof(float), 1, bin3ds);
      }break;
    case 0xA35A:
      {
        // V offset
        fread(&(mattail->ttex->voff), sizeof(float), 1, bin3ds);
      }break;
    case 0xA35C:
      {
        // Texture rotation angle
        fread(&(mattail->ttex->rot), sizeof(float), 1, bin3ds);
      }break;
    case 0x0011:
      {
        char r, g, b;
        // Read colors
        if(is_diffuse)
        {
          fread(&r, 1, 1, bin3ds); // Red component 1 byte
          fread(&g, 1, 1, bin3ds); // Green component 1 byte
          fread(&b, 1, 1, bin3ds); // Blue component 1 byte
          mattail->diffuse = long((r&0xFF)<<16) | long((g&0xFF)<<8) | long(b&0xFF);
        }
        else if(is_ambient)
        {
          fread(&r, 1, 1, bin3ds); // Red component 1 byte
          fread(&g, 1, 1, bin3ds); // Green component 1 byte
          fread(&b, 1, 1, bin3ds); // Blue component 1 byte
          mattail->ambient = long((r&0xFF)<<16) | long((g&0xFF)<<8) | long(b&0xFF);
        }
        if(is_specular)
        {
          fread(&r, 1, 1, bin3ds); // Red component 1 byte
          fread(&g, 1, 1, bin3ds); // Green component 1 byte
          fread(&b, 1, 1, bin3ds); // Blue component 1 byte
          mattail->specular = long((r&0xFF)<<16) | long((g&0xFF)<<8) | long(b&0xFF);
        }
      }break;
    default:
      {
        unsigned long pos;
        pos = ftell(bin3ds);
        if((pos - 6) >= count) // Check if v've crossed the chunk bound.
        {
          fseek(bin3ds, -6, SEEK_CUR);
          done = 1;
          break;
        }
        // Unknow CHUNK ID
        pos += (llen - 6);
        if(fseek(bin3ds, pos, SEEK_SET)) done = 1;
      }
    }
  }
}
void read_mesh(DWORD len)
{
  unsigned long count=ftell(bin3ds) + (len - 6);
  WORD id;
  DWORD llen;
  int done = 0;
  while(!done)
  {
    id = ReadInt();
    if(feof(bin3ds)) { done = 1; break; }
    llen = ReadLong();
    switch(id)
    {
    case 0x4100: 
      {
        if(tail == NULL) break;
      }break;
    case 0x4110:
      {
        int i;
        tail->nv = ReadInt(); // No. of vertices
        tail->vlst = new float[tail->nv * 3];
        // Read vertices
        for(i=0; inv; i++)
        {
          fread(&(tail->vlst[i*3]), sizeof(float), 1, bin3ds);   
          fread(&(tail->vlst[i*3+2]), sizeof(float), 1, bin3ds);  // Swap z and y
          fread(&(tail->vlst[i*3+1]), sizeof(float), 1, bin3ds);
        }
      }break;
    case 0x4120:
      {
        int i;
        unsigned int nf;
        nf = ReadInt(); // No. of faces
        tail->nf = nf; 
        tail->flst = new WORD[tail->nf * 4];
        // Read all the faces
        for(i=0; inf; i++)
        {
          fread(&(tail->flst[i*4+2]), sizeof(WORD), 1, bin3ds);   // clock wise order
          fread(&(tail->flst[i*4+1]), sizeof(WORD), 1, bin3ds);  // worth experiment'n
          fread(&(tail->flst[i*4+0]), sizeof(WORD), 1, bin3ds);
          fread(&(tail->flst[i*4+3]), sizeof(WORD), 1, bin3ds);  // face order
        }
      }break;
    case 0x4130:
      {
        // Material mapping Info.
        int i=0;
        char ch;
        if(tail == NULL) break;
        if(tail->fhead == NULL)
        {
          tail->fhead = new face_mat;
          tail->ftail = tail->fhead;
        }
        else
        {
          tail->ftail->next = new face_mat;
          tail->ftail = tail->ftail->next;
        }
        tail->ftail->next = NULL;
        // Read material name
        while((ch = fgetc(bin3ds)) != 0)
        {
          tail->ftail->name[i] = ch;
          i++;
        }
        tail->ftail->name[i] = '\0';
        // Read no. of faces for this material
        tail->ftail->ne = ReadInt();
        tail->ftail->faces = new WORD[tail->ftail->ne];
        // read all faces (actually indices to the face list)
        fread(tail->ftail->faces, sizeof(WORD)*tail->ftail->ne, 1, bin3ds);
      }break;
    case 0x4140:
      {
        // Material mapping coords
        if(tail == NULL) break;
        int i;
        tail->mnv = ReadInt(); // No. of mapping coords
        tail->mc = new float[tail->mnv * 2];
        // Read mapping coords
        // These are actually texture coords for vertices.
        for(i=0; imnv; i++)
        {
          fread(&(tail->mc[i*2]), sizeof(float), 1, bin3ds); // U
          fread(&(tail->mc[i*2+1]), sizeof(float), 1, bin3ds);  // V
        }
      }break;
    case 0x4160:
      {
        // Local transformation matrix
        int i, j;
        if(tail == NULL) break;
        for (j=0;j<4;j++)
        {
          for (i=0;i<3;i++)
          {
            fread(&(tail->lmat[j][i]),sizeof (float),1,bin3ds);
          }
        }
        tail->lmat[0][3]=0;
        tail->lmat[1][3]=0;
        tail->lmat[2][3]=0;
        tail->lmat[3][3]=1;
      }break;
    case 0x4000:
      {
        // Object
        fseek(bin3ds, -6, SEEK_CUR);
        done = 1;
        break;
      }
    default: // Unknown CHUNK
      {
        unsigned long pos;
        pos = ftell(bin3ds);
        if((pos - 6) >= count)
        {
          fseek(bin3ds, -6, SEEK_CUR);
          done = 1;
          break;
        }
        pos += (llen - 6);
        if(fseek(bin3ds, pos, SEEK_SET)) done = 1;
      }
    }
  }
}
void read_object(DWORD len)
{
  unsigned long count=ftell(bin3ds) + (len - 6);
  WORD id;
  DWORD llen;
  int done = 0;
  head = tail = NULL;
  maphead = maptail = NULL;
  mathead = mattail = NULL;
  while(!done)
  {
    id = ReadInt();
    if(feof(bin3ds)) { break; done = 1; }
    llen = ReadLong(); // length of chunk
    switch(id)
    {
    case 0x4000:
      {
        // He He! MESH!
        int u=0;
        char ch;
        if(head == NULL)
        {
          head = new mesh_object;
          tail = head;
        }
        else
        {
          tail->next = new mesh_object;
          tail = tail->next;
        }
        // Initialize
        tail->next = NULL;
        tail->flst = NULL;
        tail->vlst = NULL;
        tail->nf = 0;
        tail->nv = 0;
        tail->mnv = 0;
        tail->mc = NULL;
        tail->fhead = NULL;
        tail->ftail = NULL;
        // Read mesh name (object name)
        while((ch = fgetc(bin3ds)) != 0)
        {
          tail->name[u] = ch;
          u++;
        }
        tail->name[u] = '\0';
        read_mesh(llen);
        if(tail->nv == 0)        // Object was not a mesh (might be a light etc)
        {
          // So free up the previously allocated mem (if any)
          if(tail->flst != NULL) delete tail->flst;
          if(tail->vlst != NULL) delete tail->vlst;
          if(tail == head) // check if first mesh
          {
            delete tail;
            tail = head = NULL;
          }
          else // No, then detach last and relocate tail
          {
            mesh_object *t, *p;
            t = p = head;
            while(t != NULL)
            {
              if(t == tail) break;
              else
              {
                p = t;
                t = t->next;
              }
            }
            delete tail;
            tail = p;
            tail->next = NULL;
          }
        }
      }break;
    case 0xAFFF: read_mat(llen); break;  // Read materials
    default: // Unknown
      {
        unsigned long pos;
        pos = ftell(bin3ds);
        if((pos - 6) >= count)
        {
          fseek(bin3ds, -6, SEEK_CUR);
          done = 1;
          break;
        }
        pos += (llen - 6);
        if(fseek(bin3ds, pos, SEEK_SET)) done = 1;
      }
    }
  }
}
int read_3ds()
{
  WORD id;
  DWORD len;
  int done = 0;
  while(!done)
  {
    id = ReadInt();
    if(feof(bin3ds)) { break; done = 1; }
    len = ReadLong();
    switch(id)
    {
    case 0xFFFF: done = 1; break;
    case 0x3D3D: read_object(len); break; // Read Objects
    default: // Unknown
      {
        unsigned long pos;
        pos = ftell(bin3ds);
        pos += (len - 6);
        if(fseek(bin3ds, pos, SEEK_SET)) done = 1;
      } break;
    }
    if(feof(bin3ds)) done = 1;
  }
  return 1;
}

int read_primary_chunk (void)
{
  unsigned char version;
  
  if (ReadInt ()==0x4D4D)
  {
    fseek (bin3ds,28L,SEEK_SET);
    version=ReadChar ();
    if (version<3)
    {
      // Invalid version
      return 1;
    }
    fseek (bin3ds, 16, SEEK_SET); // Relocate to chunk start
    read_3ds();
  }
  else
    return (1);
  
  return (0); 
}
int load_3ds(FILE *fp)
{
  char buf[6] = ".PMF";
  WORD ver = 0x0002;
  unsigned long sz;
  int st;
  if(fp == NULL) return -1;
  bin3ds = fp;
  fseek(bin3ds, 0, SEEK_SET); // Just to make sure 
  while (read_primary_chunk ()==0);
        // TODO: IMPORTANT!!!!!!
        // Free all the linked list here after u do watever u want to do 
        // with the obj data (i.e u could write the data to a custom format file.
  // I use my own mesh format)
  return (0);
}

// Code end here

Discuss this article in the forums

Date this article was posted to GameDev.net: 12/18/2000
(Note that this date does not necessarily correspond to the date the article was written)

See Also:
Sweet Snippets

© 1999-2011 Gamedev.net. All rights reserved. Terms of Use Privacy Policy
Comments? Questions? Feedback? Click here!